Offshore pipelines laid along the seafloor for the delivery of oil and gas from a source to an ultimate destination are manufactured of short joints of pipe as a manufacturing reality. These joints of pipe must be connected together in order to make a pipeline. The cost it takes to make the connection is a factor of the cost of the connection, the time it takes to make the connection, and the time it takes to do any required coating after the connection is made. A major portion of the costs was simply the vessel time charge to make the connections.
Historically the connections have been made by welding the joints of the pipe together on a barge. The efficiency of this process was improved by providing multiple stations spaced along a horizontal deck so that several workers could be making a portion of the welds at the same time. An added station for coating made this a concurrent time also. These barges are referred to as “S” lay as the pipe comes off horizontally, bends downwardly towards the seafloor across a stinger, and then reverse bends onto the seafloor, resembling an “S”.
More recently a J-Lay method has been used which uses and inclined tower so that the pipe departs the vessel in line with the tower and makes a single bend onto the ocean floor.
More recently yet, long sections of pipe have been welded together at lower cost on shore, and then simply reeled together onto a reel barge. To envision this, you need to imagine a twenty-four-inch diameter pipe being rolled up on a very large spool like a hose. The speed of simply unrolling the pipe offshore made this a very fast operation, which easily overcame the higher vessel cost. This is especially true in longer pipelines where the connection time accumulates. A problem with this method is that in some cases the pipelines tend to be buoyant and need to be weighed down. The typical weight is a layer of concrete, which will not bend.
Shorter and infield pipelines typically do not justify the high mobilization costs and daily rate of a reel type barge method. They are more economic with the balance of higher joint connection costs but lower vessel and mobilization costing. As a comparison, the mobilization cost of a modern reel pipelay vessel to a remote location can exceed the capital cost of a simpler jointed laying system placed on a local barge.
On the jointed laying systems, a connection has to be made, it typically has to be inspected, it has to be pressure tested, and the connection has to be coated. In a lower cost J-Lay type systems, each of these events must happen in sequence, so connection time can be a majority of the cost of the pipe laying other than the pipe itself.
Some solutions have been proposed to speed the connection and handling operations from forging to welding specially prepared connectors on each end of the joint of pipeline for quick make-up. The have characteristically required a specialty connector half to be welded to both ends of the pipe sections in preparation for the fast make-up.
Since the inception of pipelaying of any kind, and especially since the inception of J-Lay style pipeline laying, a need for a low-cost connector which will rigidly and assuredly connect the joints of pipeline together without a specially prepared end to be mated with has been needed. Additional needs have been connectors with rapid testing and elimination of X-Ray or ultrasonic inspections at the connection site on the rig for quality assurance.